DNA clues shed light on woolly mammoth death

Scientists at the University of California, Berkeley, have discovered indications as to why the woolly mammoth became extinct by examining ancient DNA. Researchers have concluded the animals died out because their genomes developed in ways not conducive to survival.

Genetic mutations found in mammoth DNA from 4,000 years ago was compared to another genetic sample from 45,000 years ago. Dr Rebekah Rogers, who led the research, said of this method: “It’s difficult to catch a population in the process of going extinct, but this study finally made it possible, thanks to advances in DNA sequencing.”

Comparing the samples revealed that the last mammoths, living on Wrangel Island in the Arctic Ocean, had lost receptors key for their sense of smell and had developed anti-social behaviour. Such mutations affected the breeding rate of the animals on the island, leading to their extinction. By the time of the mammoth’s nadir, they had also lost their thick coats, making them unsuited to the harsh winters of Siberia. Scientists also found the animals lacked levels of protein in their urine necessary for attracting a mate, as well as having digestive problems that made survival harder.

Dr Rogers described the latest discovery as the first instance of “genetic meltdown” in a single species. She said the mammoth’s genetic material had been “falling apart” at the time of its extinction.

In addition to providing a crucial insight into the demise of the woolly mammoth, this research is being hailed as a turning point for work into conservation. The scientific community have said the research could be a breakthrough for current conservation work regarding saving animals like the white rhino, Indian elephant, and panda.

Love Dalen, an academic in evolutionary genetics at the Swedish Museum of Natural History called the research “very novel” and speculated about the “important implications for conservation biology” that could result from examining genomes from other species in a similar fashion. Dalen, who pioneered work into the DNA sequencing of mammoths, discovered deletions in the genes of the animals, whereby “big chunks” of genomes were missing.

Dr Rogers said her team’s research shows “when you have these small populations for an extended period of time they can go into genomic meltdown.” The key then is to prevent such meltdowns from occurring in the first place by making sure populations of rare animals do not dip to such low levels that genetic mutations occur.

Dr Rogers explained that “if you have a small population and then bring it back up to larger numbers” species may not be able to be saved from the threat of extinction as the species “will still bear those signatures of this genomic meltdown.”